Background. The striking analogies between the ideas of Freud and Frie
drich Nietzsche, whose works were published from one to three decades
before those of Freud, have been commented upon, but no previous syste
matic correlation of the ideas of Nietzsche and Freud has been made. M
ethod. The major works of Nietzsche were read, and each possible analo
gy to an idea later broached by Freud was correlated by a systematic r
eview of his works. Any references to Nietzsche in Freud's writings an
d reported conversation were culled. Results. Concepts of Nietzsche wh
ich are similar to those of Freud include (a) the concept of the uncon
scious mind; (b) the idea that repression pushes unacceptable feelings
and thoughts into the unconscious and thus makes the individual emoti
onally more comfortable and effective; (c) the conception that repress
ed emotions and instinctual drives rater are expressed in disguised wa
ys (for example, hostile feelings and ideas may be expressed as altrui
stic sentiments and acts); (d) the concept of dreams as complex, symbo
lic ''illusions of illusions'' and dreaming itself as a cathartic proc
ess which has healthy properties; and (e) the suggestion that the proj
ection of hostile, unconscious feelings onto others, who are then perc
eived as persecutors of the individual, is the basis of paranoid think
ing. Some of Freud's basic terms are identical to those used by Nietzs
che. Conclusion. Freud repeatedly stated that he had never read Nietzs
che. Evidence contradicting this are his references to Nietzsche and h
is quotations and paraphrases of him, in casual conversation and his n
ow published personal correspondence, as well as in his early and late
r writings.